The purpose of the proposed project is to identify and characterize lumbar ventral spinocerebellar tract (VSCT) neurons which have collaterals to the cervical enlargement. Such propriospinal-VSCT neurons will be identified using a double-retrograde labeling protocol. Horseradish peroxidase (HRP) will be used to label lumbar spinocerebellar neurons and tritiated inactivated HRP (H3-apo-HRP) will be used to label lumbar neurons with terminals in the cervical enlargement. Lumbar cells labeled by both substances will be considered propriospinal-VSCT neurons. With intracellular recording techniques, the responses of identified VSCT neurons to graded electrical stimulation of select hindlimb muscle and cutaneous nerves will be used to characterize their physiological properties. Their position in the lumbar cord will then be identified by intracellular labeling with HRP. When coupled with retrograde labeling of long ascending propriospinal neurons using H3-apo-HRP, propriospinal-VSCT neurons will be identified by being doubly-labeled. The physiological properties of these neurons can then be comparied. The results of this study are expected to be significant to basic scientists concerned with developing testable hypotheses of neural mechanisms for interlimb control during movement. For clinical scientists these results are expected to be significant in the diagnosis and treatment of patients with disorders of movement affecting major ascending spinal pathways, such as Friedreich's ataxia.